Reciprocating compressor with unloading and capacity modulating control



y 1951 D. c. RINEHART RECIPRQCATING COMPRESSOR WITH UNLOADING ANDCAPACITY MODULATING CONTROL Filed Jan. :51, 1948 Fig.1.

r 4 Invehtpr: Dean C.Rineh ar't l-lis Attorney.

Patented May 29, 1951 RECIPROCATING COMPRESSOR WITH UN- LOADING ANDCAPACITY MODULATING CONTROL Dean 0. Rinehart, Fort Wayne, Ind., assignorto General Electric Company, a. corporation of New York ApplicationJanuary 31, 1948, Serial No. 5,645

This invention relates to gas compressors of the reciprocating type andparticularly to devices for unloading such compressorsand for providingmodulation of the compressor capacity.

In the operation of refrigerant compressors, for example, such as thoseemployed in air conditioning systems, it is frequently desirable toprovide a control which makes it possible to vary the capacity of thecompressor in accordance with the demands of the system, and preferablysuch variation is effected over a relatively wide range in gradualsteps. It is also desirable that a simple and effective unloading devicebe provided so that the compressor may be started under no-loadconditions. Accordingly, it'is an object of this invention to provide acompressor of the reciprocating type including an improved arrangementfor unloading the compressor and for modulating the capacity thereof.

It is another object of the invention to provide a capacity modulatingdevice for compressors of the reciprocating type which shall be ofsimple construction and readily controllable.

Further objects and advantages of thisinvention will become apparent asthe following 8 Claims. (Cl. 230-24) description proceeds, and thefeatures of novelty which characterize the invention will be pointed outwith particularity in the claims annexed to and forming a part of thisspecification.

For a better understanding of the invention reference may be had to theaccompanying drawing in which Fig. 1 is a diagrammatic view illustratingan air cooling system provided with a refrigerant compressor embodyingthe invention; Fig. 2 is an enlarged sectional view of the compressorshown in Fig. 1; and Fig. 3 is an end elevation view of the compressor.

The air cooling system shownin Fig. 1 comprises a refrigerant evaporator4 arranged in a duct 5 through which air to be cooled is cir-' culatedby operation of a suitable blower (not shown). Liquid refrigerant in theevaporator is vaporized by the absorption of heat from the aircirculated through the duct, and the vaporized refrigerant is withdrawnthrough a suction line 6 by operation of a reciprocating compressor 1driven through a belt 8 by an electric motor 9. The refrigerant iscompressed and discharged from the compressor and conducted to an aircooled condenser Ill having an air circulating fan II driven by a motorI2. The hot compressed refrigerant is cooled in the condenser .andliquefied and. flows to a liquid receiver l3 from which it is returnedto the evaporator through a liquid line 4. u d ntro is; a Penman? e p???c V 2 sion valve 15. The valve I5 is provided with a temperatureresponsive bulb or feeler element [511 secured in heat exchange with thesuction line 6 and operates to maintain a predetermined amount ofsuperheat in the vaporized refrigerant withdrawn from the evaporator.During the operation of the air cooling system it is desirable that themotor compressor unit be operated at a relatively high coeflicient ofperformance. The coefficient of performance may be improved bypreventing short cycling of the motor 9, that is, by operating thecompressor at a capacity such that under low-loadconditions, forexample, it will operate over an extended period to maintain the desiredpressures in the system rather than operating at high capacity for shortperiods. Short cycling is objectionable because frequent starting andstopping of the electric motor tends to overheat the motor. In thesystem shown in Fig. 1 a control It responsive to the head pressure ofthe compressor 1 is arranged to actuate a solenoid valve l1 and vary thecapacity of the compressor in a manner to be described below. Thedetails of construction of the'compres'sor and the arrangement of thecapacity modulating and unloading device are clearly shown in Figs. 2and 3. The compressor comprises a cylinder block I8 mounted on acrankcase l9. Cylinders 20 are formed within the block i8 and are closedby a compressor head structure including a valve plate 2| and a head 22secured to the block by bolts 23. Within the cylinders '20 there aremounted cylinder sleeves 24 which are vertically slidable within thecylinders and within which pistons 25 are reciprocated by operation of acrankslfift 26 journaled in bearings in the crankcase I9, the right-handbearing being mounted in a removable end plate 21. The valve plate 2| isprovided with intake valves including flexible disks ZB'and dischargevalves including flexible disks 29 for controlling intake ports 30 anddischarge ports 3| respectively. The intake valve disks 28 are providedwith suitable openings 28a so that the discharge ports 3| communicatedirectly with the cylinder space within the sleeves 24. The intake ports30 are connected in communication with the suction line 6 throughannular intake passages 32 formed between the sleeves 24 and the blockl8 and connected to the passages 30 by upright passages 33 formed asgrooves in the sleeves 24'. The annular passages 32 are formed bygrooves 34 in the walls of the cylinders 20 and annular grooves 35 inthe external walls of thesleevesz l. The lower ends 3 36 of the sleeves24 are of reduced external diameter and cooperate with the walls of thecylinders 2|] to form annular chambers 31 which are closed by collars 38rigidly secured in the lower ends of the cylinders 20 by retaining rings39. The annular chambers 31 are sealed by upper and lower resilientrings or gaskets 40 and4l. The upper gasket 40 is seated on a downwardlyfacing shoulder 42 formed by the reduced portion of the sleeve 24, andthe lower gasket is seated on the collars 38. The gaskets are pressedapart and retained in sealing engagement with the cylinder walls by ahelical spring 43 surrounding the sleeve, the gaskets being providedwith annular grooves forming seats for the spring.

In the drawing the cylinder sleeves 24 have been shown in engagementwith sealing rings or gaskets 44 embedded in the lower sideof the valveplate 2|. The sleeves are held in this position by fluid pressure withinthe chambers 3'! which opposes the force of a plurality of springs 45arranged in rings around the sleeves and seated in recesses 41 in thevalve plate and in recesses 46 in the sleeves. Only two of the springs45 have been shown in the drawing, it being unnecessary for anunderstanding or the invention that the remaining springs be illustratedThe combined force of the springs 45 is such that these springs overcomethe springs 43 and bias the sleeves 24 to their lower position so thatbypasses are provided around the'intake valves at the tops of thesleeves and the compressor is normally unloaded. The lowermost positionof the sleeves is determined by stop rings 48 formed as internal flangeson th collars 38.

A body of lubricating oil 49 is maintained in a sump formed by thebottom of 'the crankcase I9 and is circulated from the sump through aconduit 50 and a connection to a gear pump comprising a gear 52 mountedon the end of the crankshaft 25 and a meshing gear 53, these gears beingarranged in a housing to provide a gear pump in a manner well knowninthe art and which discharges the oil through a duct 54 to oilcirculating passages indicated generally by dotted lines in the crank 26and'in the connecting rods indicated at 55. The lubricant is alsoemployed as the pressure fluid for actuating the sleeves 24, andalthough the same pump maybe employed it is preierr'ed,'as shown in thedrawing, to provide'a separate pump comprising intermeshing gears 56 and51, the gear 56 being connected directly by'a stub shaft'58 to thegear53. Oil from the conduit 50 enters the second pump through aconnection55 andbybperation of the gears 56 and 51, is pumped throughadi'scharge conduit 60 and entersbra'nc h' conduits Bl and 52 leading tothe annular "chambers'3l of the left-hand'and right-hand cylindersrespectively. The valve 11 is arranged to controlthe flow of oil throughthe branch conduit 61 This valve is normally open but may be'clo'sed byenergization of a solenoid '63 to cutoff the supply of oil underpressure to the left-hand chamber 31. Bleeder passages 84 are providedin the walls of the sleeves '24 'betweenthe'passa'ges "3'1 and theinside walls 'of the cylinderjsleeves 'so that a minimum fiow of oil ispermitted and provides lubrication for the pistons. A minimum openingmay be provided in the valve l1 so that even when the valve isinjitsfclosed position'there is a flow of oil'through bleede'rs64for'lubricat ing purposes. These bleeder passages'al'so limit the backpressure on the g'ear pump. v

When the compressor is at astandstill' there is 4 no oil pressure in thechambers 31 and the sleeves 24 are pressed downwardly by the springs 45to open the bypasses over the tops of the sleeves, this being theunloaded position. When the com pressor is started, oil pressure isgradually built up in both chambers 31, the valve I! being normallyopen, ahd when a predetermined speed has been reached the pressure issufficient to force the sleeves against the gaskets 44 and maintain themin this position to seal oil the bypass and load the compressor. As theconditions of operation change it may become desirable to decrease thetotal compressor capacity and this may be done by closing the valve llto open the bypass in the left-hand cylinder and unload that cylinder.In order to control the valve ll the control [5 is arranged to actuate asnap-acting switch 65 upon expansion of a bellows 66 connected through aduct 67 in communication with the discharge chamber in the head 22 ofthe compressor. When the head pressure reaches a predetermined highvalue the bellows expands and moves the switch 55 to its closed positionthereby energizing the solenoid 63 and blosing the valve ll. This cutsoff the main supply of oil to the left-hand chamber 37 and unloads theleft-hand cylinderby allowing the springs 45 to move the sleeve 24 awayfrornits seat. The actuation of the control Hi to efiect loadingandunloading of the left-hand cylinder provides modulation of thecapacity of the compressor, the cylinder being loaded aga'in as soon asthe head pressure falls to a predetermined value at which thesnap-acting switch is moved to its open position and deenergizes thesolenoid. Whenever the compressor is stopped the oil pressure fallsbecauseof the stopping of theoperation of the oil pumps, and thepressure in the chambers 31 drops to allow the springs 45 to force bothcylinder sleeves 24 away from their seats and unload 'the compressor.Obviously the control l5 may 'be actuated in'accordance with anycondition of operation of the refrigerating system which is indicativeofthe required cornpressor capacity so that modulation of thecompressormay be efiecte'd. in accordance with changes in the selectedcondition,the control in response to head pressure having been selected merely byway of illustration. It is also obvious that althougha two-cylindercompressor hasbeen illustrated the invention is applicable tomulticylinder compressors regardless of the number of cylinders andthatwith "more than twocylinders the modulating control may be arrangedfor successive operation of the bypass control of the cylinders, apluralityof the cylinders being 'provided with valves forcontrollihgtheflow-ofoil thereto.

Although this invention has been described in connection with atwoecylinder compressor having capacity modulation control of-on'ly oneof the cylinders, various modifications will occur to those skilled inthea'rt. It is not,'therefore, de sired that the invention be limited-tothe particular details illustrated and described and it is intended bythe appended claims to cover all modifications within the spirit andscope-of --the invention.

What I claim as new and desire tosecure'by Letters Patent of the UnitedStatesis:

1. A compressor of thereciprocating typecomprising a cylinder blockhaving a cylinder-therein, a piston mounted'forreciprocation in saidcylinder, intakeandex "valves forsaid cylinder, a sleeve valve siirQounding said piston and movable between open and closed positions,saidsleeve valve in its open position providing a bypassaround saidintake valve, means biasing said sleeve valve toward its open position,meansincluding an annular shoulder on said sleeve valve for forming anannular chamber surrounding said piston whereby said chamber expandsupon movement of said sleeve valve toward its closed position, and meansfor supplying to said chamber a fluid under pressure for expanding saidchamber and moving said sleeve valve toward its closed position toclosesaid bypass and control the loading of said cylinder.

2. 'A compressor of the'reciprocating type coni prising a cylinderblock, means providing a head for said block, a cylinder sleevecooperating with said head to form a closed cylinder and mounted in saidblock for movement toward and away from said head, a piston in saidcylinder, means for driving said piston, intake and exhaust valves forsaid cylinder, an annular seat on said head for limiting the movement ofsaid sleeve toward said head and for sealing said cylinder, means forurging said sleeve away from said seat to provide a bypass around saidintake valve, an expansible chamber device for moving said sleeve towardsaid seat, and means including a pump driven by said driving means forsupplying fluid under pressure to said device to move said sleeve towardsaid seat and close said bypass to control the loading of said cylinder.

3. A compressor of the reciprocating type comprising a cylinder block,means providing a head for said block, a cylinder sleeve cooperatingwith said head to form a closed cylinder and mounted in said block formovement toward and away from said head, a piston in said cylinder,means for driving said piston, intake and exhaust valves for saidcylinder, an annular seat on said head for limiting the movement of saidsleeve toward said head and for sealing said cylinder, means for urgingsaid sleeve away from said seat to provide a bypass around said intakevalve, means providing an annular chamber expansible longitudinally ofsaid cylinder for moving said sleeve toward said seat, and meansincluding a pump driven by said driving means for supplying a fluidunder pressure to said chamber to move said sleeve toward said seat andclose said bypass to control the loading of said cylinder.

4. A compressor of the reciprocating type comprising a cylinder blockhaving a cylinder therein, a head for said block arranged to close saidcylinder, a cylinder sleeve slidably mountedin said cylinder formovement toward and away from said head, a piston mounted in saidsleeve, said sleeve being formed with an external annular shoulder facinaway from said head and forming an annular chamber between said sleeveand the wall of said cylinder, annular closure means spaced from saidshoulder for closing said chamber, intake and discharge valvescommunicating with the interior of said sleeve, means for urging saidsleeve away from said head to provide a bypass around said intake valve,and means for admitting fluid under pressure to said chamber for movingsaid sleeve toward said head to close said bypass and control theloading of the compressor.

5. A compressor of the reciprocating type comprising a cylinder blockhaving a cylinder therein, a head for said block arranged to close saidcylinder, a cylinder sleeve slidably mounted in said cylinder formovement toward and away from said head, a piston mounted in saidsleeve,

said sleeve being formed with an external-annular shoulder facing awayfrom saidheadand forming an annular chamber between said sleeve and thewall of said cylinder, annular closure means spaced from said shoulderfor closing said chamber, a pair of resilient annular gaskets one seatedagainst said-shoulder and th other seated against said closure means, aspring engaging said gaskets for urging said gaskets apart and formaintaining said gaskets seatedon said shoulder and closure meansregardless of movement of said sleeve, intake and discharge valvescommunicating with the interior of said sleeve, means for urging saidsleeve away from said head to provide a bypass around said intake valve,and means for admittin fluid under pressure to said chamber for movingsaid sleeve toward said head to close said bypass and control theloading of the compressor.

6. A compressor of the reciprocating type comprising a cylinder blockhaving a cylinder therein, a valve plate for closing said cylinder, acylinder sleeve slidably mounted in said cylinder for movement towardand away from said plate, a piston mounted in said sleeve, meansproviding an intake passage for said compressor extending about saidsleeve, intake and exhaust valves in said plate communicating with theinterior of said sleeve, said plate having a passage therein connectingsaid intake valve and said intake passage, means for urging said sleeveaway from said valve plate to provide a bypass around said intake valve,and fluid pressure means for moving said sleeve toward said valve plateto control said bypass and effect the loading and unloading of thecompressor.

'7. A compressor of the reciprocating type comprising a cylinder blockhaving a cylinder therein, a head for said block arranged to close saidcylinder, a cylinder sleeve slidably mounted in said cylinder formovement toward and away from said head, a piston mounted in saidsleeve, said sleeve being formed with an external annular shoulderfacing away from said head and forming an annular chamber between saidsleeve and the Wall of said cylinder, annular closure means spaced fromsaid shoulder for closing said chamber, intake and discharge valvescommunicating with the interior of said sleeve, means for urging saidsleeve away from said head to provide a bypass around said intake valve,means for retaining a body of liquid lubricant for the compressor, apump for supplying lubricant under pressure Irom said body to saidannular chamber, and means dependent upon the load on the compressor forcontrolling the supply of lubricant to said chamber to close said bypassand eifect the loading of the compressor.

8. A compressor of the reciprocating type comprising a cylinder blockhaving a cylinder therein, a head'for said block arranged to close saidcylinder, a cylinder sleeve slidably mounted in said cylinder formovement toward and away from said head, a piston mounted in saidsleeve, said sleeve being formed with an external annular shoulderfacing away from'said head and forming an annular chamber between saidsleeve and the wall of said cylinder, annular closure means spaced fromsaid shoulder for closing said chamber, intake and discharge valvescommunicating with the interior of said sleeve, means for urging saidsleeve away from said head to provide a bypass around said intake valve,means for retaining a body of liquid lubricant for the 7 compressor, apump for supplying liquid lubri-e DEA-N C. RINEHART REFERENCES CITED Thefb'll'dwing referefices' are of redrd in tfi file of this patent:

8 12mm sums PATENTS mfi f 1,668,195 1,709,906 2,074,9'fl 2,129,0732:29am 2,338,486 21387-11? Numpe;

Ndfii I iiie Aikman May 3, i928 Faifiief Apr. 23; I929 Hull Mar. 1937Shdfi sept. 6', i933 NeS'o'fi Sept. 21, 1943 Bi'idgi" Jan. 4, 1944Buc'hler" oct. 16, 1945 FOREIGN PATENTS- Country Date Great; Britain1935

